//
// AtomicCounter.h
//
// Library: Foundation
// Package: Core
// Module:  AtomicCounter
//
// Definition of the AtomicCounter class.
//
// Copyright (c) 2009, Applied Informatics Software Engineering GmbH.
// and Contributors.
//
// SPDX-License-Identifier:	BSL-1.0
//


#ifndef Foundation_AtomicCounter_INCLUDED
#define Foundation_AtomicCounter_INCLUDED


#include "Poco/Foundation.h"
#if POCO_OS == POCO_OS_WINDOWS_NT
#    include "Poco/UnWindows.h"
#elif POCO_OS == POCO_OS_MAC_OS_X
#    if __MAC_OS_X_VERSION_MAX_ALLOWED >= 101200 || __IPHONE_OS_VERSION_MAX_ALLOWED >= 100000 || __TV_OS_VERSION_MAX_ALLOWED >= 100000 \
        || __WATCH_OS_VERSION_MAX_ALLOWED >= 30000
#        if __cplusplus >= 201103L
#            ifndef POCO_HAVE_STD_ATOMICS
#                define POCO_HAVE_STD_ATOMICS
#            endif
#        else
#            include <libkern/OSAtomic.h>
#        endif
#    else
#        include <libkern/OSAtomic.h>
#    endif
#elif ((__GNUC__ == 4) && (__GNUC_MINOR__ >= 2) || __GNUC__ > 4) && (defined(__x86_64__) || defined(__i386__))
#    if !defined(POCO_HAVE_GCC_ATOMICS) && !defined(POCO_NO_GCC_ATOMICS)
#        define POCO_HAVE_GCC_ATOMICS
#    endif
#elif ((__GNUC__ == 4) && (__GNUC_MINOR__ >= 3) || __GNUC__ > 4)
#    if !defined(POCO_HAVE_GCC_ATOMICS) && !defined(POCO_NO_GCC_ATOMICS)
#        define POCO_HAVE_GCC_ATOMICS
#    endif
#endif // POCO_OS
#include "Poco/Mutex.h"
#ifdef POCO_HAVE_STD_ATOMICS
#    include <atomic>
#endif


namespace Poco
{


class Foundation_API AtomicCounter
/// This class implements a simple counter, which
/// provides atomic operations that are safe to
/// use in a multithreaded environment.
///
/// Typical usage of AtomicCounter is for implementing
/// reference counting and similar things.
///
/// On some platforms, the implementation of AtomicCounter
/// is based on atomic primitives specific to the platform
/// (such as InterlockedIncrement, etc. on Windows), and
/// thus very efficient. On platforms that do not support
/// atomic primitives, operations are guarded by a FastMutex.
///
/// The following platforms currently have atomic
/// primitives:
///   - Windows
///   - Mac OS X
///   - GCC 4.1+ (Intel platforms only)
{
public:
    typedef int ValueType; /// The underlying integer type.

    AtomicCounter();
    /// Creates a new AtomicCounter and initializes it to zero.

    explicit AtomicCounter(ValueType initialValue);
    /// Creates a new AtomicCounter and initializes it with
    /// the given value.

    AtomicCounter(const AtomicCounter & counter);
    /// Creates the counter by copying another one.

    ~AtomicCounter();
    /// Destroys the AtomicCounter.

    AtomicCounter & operator=(const AtomicCounter & counter);
    /// Assigns the value of another AtomicCounter.

    AtomicCounter & operator=(ValueType value);
    /// Assigns a value to the counter.

    operator ValueType() const;
    /// Returns the value of the counter.

    ValueType value() const;
    /// Returns the value of the counter.

    ValueType operator++(); // prefix
        /// Increments the counter and returns the result.

    ValueType operator++(int); // postfix
        /// Increments the counter and returns the previous value.

    ValueType operator--(); // prefix
        /// Decrements the counter and returns the result.

    ValueType operator--(int); // postfix
        /// Decrements the counter and returns the previous value.

    bool operator!() const;
    /// Returns true if the counter is zero, false otherwise.

private:
#if defined(POCO_HAVE_STD_ATOMICS)
    typedef std::atomic<int> ImplType;
#elif POCO_OS == POCO_OS_WINDOWS_NT
    typedef volatile LONG ImplType;
#elif POCO_OS == POCO_OS_MAC_OS_X
    typedef int32_t ImplType;
#elif defined(POCO_HAVE_GCC_ATOMICS)
    typedef int ImplType;
#else // generic implementation based on FastMutex
    struct ImplType
    {
        mutable FastMutex mutex;
        volatile int value;
    };
#endif // POCO_OS

    ImplType _counter;
};


//
// inlines
//


#if defined(POCO_HAVE_STD_ATOMICS)
//
// C++11 atomics
//
inline AtomicCounter::operator AtomicCounter::ValueType() const
{
    return _counter.load();
}


inline AtomicCounter::ValueType AtomicCounter::value() const
{
    return _counter.load();
}


inline AtomicCounter::ValueType AtomicCounter::operator++() // prefix
{
    return ++_counter;
}


inline AtomicCounter::ValueType AtomicCounter::operator++(int) // postfix
{
    return _counter++;
}


inline AtomicCounter::ValueType AtomicCounter::operator--() // prefix
{
    return --_counter;
}


inline AtomicCounter::ValueType AtomicCounter::operator--(int) // postfix
{
    return _counter--;
}


inline bool AtomicCounter::operator!() const
{
    return _counter.load() == 0;
}


#elif POCO_OS == POCO_OS_WINDOWS_NT
//
// Windows
//
inline AtomicCounter::operator AtomicCounter::ValueType() const
{
    return _counter;
}


inline AtomicCounter::ValueType AtomicCounter::value() const
{
    return _counter;
}


inline AtomicCounter::ValueType AtomicCounter::operator++() // prefix
{
    return InterlockedIncrement(&_counter);
}


inline AtomicCounter::ValueType AtomicCounter::operator++(int) // postfix
{
    ValueType result = InterlockedIncrement(&_counter);
    return --result;
}


inline AtomicCounter::ValueType AtomicCounter::operator--() // prefix
{
    return InterlockedDecrement(&_counter);
}


inline AtomicCounter::ValueType AtomicCounter::operator--(int) // postfix
{
    ValueType result = InterlockedDecrement(&_counter);
    return ++result;
}


inline bool AtomicCounter::operator!() const
{
    return _counter == 0;
}


#elif POCO_OS == POCO_OS_MAC_OS_X
//
// Mac OS X
//
inline AtomicCounter::operator AtomicCounter::ValueType() const
{
    return _counter;
}


inline AtomicCounter::ValueType AtomicCounter::value() const
{
    return _counter;
}


inline AtomicCounter::ValueType AtomicCounter::operator++() // prefix
{
    return OSAtomicIncrement32(&_counter);
}


inline AtomicCounter::ValueType AtomicCounter::operator++(int) // postfix
{
    ValueType result = OSAtomicIncrement32(&_counter);
    return --result;
}


inline AtomicCounter::ValueType AtomicCounter::operator--() // prefix
{
    return OSAtomicDecrement32(&_counter);
}


inline AtomicCounter::ValueType AtomicCounter::operator--(int) // postfix
{
    ValueType result = OSAtomicDecrement32(&_counter);
    return ++result;
}


inline bool AtomicCounter::operator!() const
{
    return _counter == 0;
}

#elif defined(POCO_HAVE_GCC_ATOMICS)
//
// GCC 4.1+ atomic builtins.
//
inline AtomicCounter::operator AtomicCounter::ValueType() const
{
    return _counter;
}


inline AtomicCounter::ValueType AtomicCounter::value() const
{
    return _counter;
}


inline AtomicCounter::ValueType AtomicCounter::operator++() // prefix
{
    return __sync_add_and_fetch(&_counter, 1);
}


inline AtomicCounter::ValueType AtomicCounter::operator++(int) // postfix
{
    return __sync_fetch_and_add(&_counter, 1);
}


inline AtomicCounter::ValueType AtomicCounter::operator--() // prefix
{
    return __sync_sub_and_fetch(&_counter, 1);
}


inline AtomicCounter::ValueType AtomicCounter::operator--(int) // postfix
{
    return __sync_fetch_and_sub(&_counter, 1);
}


inline bool AtomicCounter::operator!() const
{
    return _counter == 0;
}


#else
//
// Generic implementation based on FastMutex
//
inline AtomicCounter::operator AtomicCounter::ValueType() const
{
    ValueType result;
    {
        FastMutex::ScopedLock lock(_counter.mutex);
        result = _counter.value;
    }
    return result;
}


inline AtomicCounter::ValueType AtomicCounter::value() const
{
    ValueType result;
    {
        FastMutex::ScopedLock lock(_counter.mutex);
        result = _counter.value;
    }
    return result;
}


inline AtomicCounter::ValueType AtomicCounter::operator++() // prefix
{
    ValueType result;
    {
        FastMutex::ScopedLock lock(_counter.mutex);
        result = ++_counter.value;
    }
    return result;
}


inline AtomicCounter::ValueType AtomicCounter::operator++(int) // postfix
{
    ValueType result;
    {
        FastMutex::ScopedLock lock(_counter.mutex);
        result = _counter.value++;
    }
    return result;
}


inline AtomicCounter::ValueType AtomicCounter::operator--() // prefix
{
    ValueType result;
    {
        FastMutex::ScopedLock lock(_counter.mutex);
        result = --_counter.value;
    }
    return result;
}


inline AtomicCounter::ValueType AtomicCounter::operator--(int) // postfix
{
    ValueType result;
    {
        FastMutex::ScopedLock lock(_counter.mutex);
        result = _counter.value--;
    }
    return result;
}


inline bool AtomicCounter::operator!() const
{
    bool result;
    {
        FastMutex::ScopedLock lock(_counter.mutex);
        result = _counter.value == 0;
    }
    return result;
}


#endif // POCO_OS


} // namespace Poco


#endif // Foundation_AtomicCounter_INCLUDED
